Flow-through capacitor

ABSTRACT

A flow-through capacitor and a controlled charge chromatography column system using the capacitor for the purification of a fluid-containing material, which column comprises an inlet for a fluid to be purified and an outlet for the discharge of the purified fluid, and a flow-through capacitor disposed within the column. The flow-through capacitor comprises a plurality of spirally-wound, stacked washer or rods to include a first electrically conductive backing layer, such as of graphite, and a first high surface area conductive layer secured to one side of the backing layer, such as carbon fibers, and a second high surface area conductive layer secured to the opposite side of the backing layer, the high surface area material layers arranged to face each other and separated by a nonconductive, ion-permeable spacer layer to insulate electrically the backing and conductive layer. The system includes a DC power source to charge the respective conductive layers with different polarities whereby a fluid-containing material passing through the column is purified by the electrically conductive, high surface area stationary phase and the retention thereof onto the high surface area layer and permitting, for example, the purification of aqueous solutions of liquids, such as salt, and providing for the recovery of a purified liquid.

REFERENCE TO PRIOR APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 08/027,699, filed Mar. 8, 1993, now U.S. Pat. No. 5,360,590which is a divisional of U.S. patent application Ser. No. 07/819,828,filed Jan. 13, 1992, now U.S. Pat. No. 5,200,068, issued Apr. 6, 1993,which is a continuation-in-part application of U.S. patent applicationSer. No. 07/792,902, filed Nov. 15, 1991, now U.S. Pat. No. 5,192,432,issued Mar. 9, 1993, which is a continuation of U.S. patent applicationSer. No. 07/512,970, filed Apr. 23, 1990, now abandoned. U.S. patentapplication Ser. No. 07/760,752, a divisional application of U.S. patentapplication Ser. No. 07/512,970, was filed on Sep. 16, 1991 and is nowU.S. Pat. No. 5,196,115, issued Mar. 23, 1993. All of these patents andthe application are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

The prior patents are directed to a flow-through capacitor and the useof the flow-through capacitor in a controlled charge chromatographiccolumn and system and to a method of operation of the flow-throughcapacitor and chromatographic system, all directed to the purificationof liquids. In one embodiment, the flow-through capacitor comprises aspirally-wound flow-through capacitor comprising a plurality of adjacentlayers, and typically, wound about a porous, nonconductive tube andcontaining anode and cathode leads adapted to be connected to a DC powersupply to provide for activation of the anode and cathode. In anotherembodiment, the invention is directed to a flow-through capacitor in astacked column form about a central porous nonconductive tube and alsofor use in a chromatographic column and system for the purification ofliquids. Both the spirally-wound and the stacked column flow-throughcapacitors are adapted to be placed within a housing with an inlet forthe introduction of a liquid to be purified and an outlet for thedischarge of a purified liquid and a concentrated liquid.

The flow-through capacitor comprises: a plurality of adjacent,alternative layers of a spacer layer comprising a non-electricallyconductive, ion-porous spacer, such as nylon cloth, to permit the flowof liquid therethrough; an electrically conductive backing layer, suchas graphite foil, and a high surface area layer on the conductivebacking layer comprising a high surface area, electrically conductivelayer, such as activated carbon, to act as the stationary phase, forexample, of a chromatographic column. As disclosed, a plurality of thelayers are first and second spacer layers, backing layers and surfacearea layers arranged in a spiral or a stacked column form housing andthen anode and cathode leads connected, e.g. integrally andrespectively, to the first and second backing layers, and to a DC powersource to provide separate and opposite electrical charges on thebacking layers and on the high surface area layers. The fluid is passedthrough the flow-through capacitor, such as, for example, an aqueoussalt solution, to provide for the recovery of a concentrated salt and apurified liquid.

It is desirable to provide for a new and improved flow-throughcapacitor, chromatographic system and method to simplify theconstruction and manufacture of the flow-through capacitor, system andmethod and which provides for an increased efficiency in thepurification of fluids.

SUMMARY OF THE INVENTION

The present invention relates to a flow-through capacitor and method ofmanufacture and operation and a chromatographic system and methodemploying the flow-through capacitor for the purification of fluids.

The invention concerns a flow-through capacitor for use in theelectrical separation of a fluid, such as for example, but not limitedto, a liquid containing one or more ionic components therein to beseparated or concentrated, and which flow-through capacitor comprises aporous, first high surface area, electrically conductive material to actas an anode and a porous, second high surface area, electricallyconductive material to act as a cathode. The capacitor also includes anionically conductive or permeable, electrically insulating spacermaterial between the first and second high surface area materials toisolate electrically the first and second, high surface area materials.The first and second high surface area materials are configured in theflow-through capacitor to face directly each other with only the spacermaterial intervening. The flow-through capacitor also includeselectrical leads adapted to connect the anode and cathode of therespective high surface area materials to a source of electrical power,and typically includes a housing to contain the flow-through capacitorwith an inlet to direct a fluid to be separated into the flow-throughcapacitor and into the space between the first and second high surfacearea materials of the capacitor, and an outlet to recover the separated,purified fluid stream and a concentrated fluid stream.

It has been discovered that a significant and surprising improvement inthe efficiency of the electrical separation or purification of a fluidis accomplished when the geometry of the flow-through capacitor isdesigned such that the first and second high surface area layersdirectly face each other across only an insulating spacer layer withoutthe employment of a conductive backing layer interposed therebetween.Optionally, where a conductive backing layer is employed, theflow-through capacitor includes electrically conductive backing materiallayers having opposite sides and with the first and second electricallyconductive high surface area materials disposed respectively and securedto the opposite sides of a pair of the conductive backing material toproduce a flow-through capacitor which includes adjacent layers, eitherin spiral, stacked, rod or robe form or in other geometry form,comprising a first high surface area material and electricallyconductive backing material and a second high surface area material andan electrically nonconductive spacer material adjacent either side ofthe first high surface area material and the second high surface areamaterial to form an anode-cathode unit of the flow-through capacitor.

A wide variety of different geometries may be employed in theflow-through capacitor consistent with having the high surface areamaterial representing the anode and cathode pairs of each anode-cathodeunit facing each other as alternating anode-cathode pairs to enhance thequality and efficiency of the electrical fluid separation. The anode andcathode units may be partially or completely enclosed employingelectrically conductive backing layers with the high surface areamaterial generally in layer form facing each other or by omitting theelectrically conductive backing layer material entirely and using thefirst and second high surface area material, an anode-cathode ofenhanced or intrinsically greater electrical conductivity. Since theproportion of the high surface area material or layer is increased inthe present geometry relative to the optional use of electricallyconductive backing layers and insulating spacer materials and layers,the amount of either required is also reduced, which permits a morecompact geometry and allows the anode and cathode layers to be closer toeach other; therefore, diminishing harmful, internal resistance of theflow-through capacitor. It has been discovered that a flow-throughcapacitor of this type of geometry provides for increased speed ofpurification of the fluids therethrough and with an increase in theefficiency of the fluid purification.

The invention also includes a method for the purification of a fluidcontaining one or more ionic components therein by electrical separationand which method comprises introducing a fluid, particularly a liquidhaving one or more ionic components therein to be removed or reduced inconcentration, into the inlet of a housing which contains a flow-throughcapacitor as described, with the anode and cathode of each anode-cathodeunit in the flow-through capacitor electrically connected to a DC powersupply to provide a controlled charge on the anode-cathode layers in theflow-through capacitor. The method includes passing the liquid to bepurified between the direct facing anode-cathode layers and within thespacer material, while the anode and cathode have different charges topermit controlled charge absorption of one or more of the ionicmaterials in the fluid to be purified onto the one or both high surfacearea materials; and discharging the purified fluid from the outlet ofthe housing and removing periodically a concentrated liquid containingthe absorbed ionic materials. The method is particularly adapted to theemployment of an aqueous solution containing one or more ionic salts toprovide a purified aqueous solution with removal or reduction orseparation of one or more of the ionic salts in the solution.

The high surface area conductive material employed in the flow-throughcapacitor may be employed in various forms, but usually is employed inlayer-type form. The high surface area material useful in the practiceof the invention may comprise a wide variety of electrically conductivematerials, alone or in combination, such as, but not limited to:activated carbon in particle, fiber, or mixtures thereof; activatedcarbon particles bonded or retained together with a binder material toform a continuous high surface area material; woven or non-wovenactivated carbon fibrous sheets or cloth; compressed, activated carbonparticles or fibers; or metal, electrically conductive particles. Thehigh surface area material may include one or more electricalconductivity enhancing additives or treatments, such as the use ofactivated carbon fibers or particles coated or plated with a conductivematerial of metal like palladium or platinum series black. For example,one high surface area material comprises compressed, activated carbonparticles or fibers or mixtures with homogeneous mixed conductivityenhancers, such as graphite, acetylene black, noble metals or noblemetal plated materials, fullerenes, or conductive ceramics or conductivepolymers. In another example, the high surface area material maycomprise a woven carbon fiber cloth with activated carbon strandsinterwoven or admixed with strands of a material of enhanced electricalconductivity, including graphite fibers, noble metals and conductivepolymers. The high surface area material may include conductiveceramics, conductive polymers, fullerene material, azite and otherconductive material. The electrical conductivity of the high surfacearea material may be enhanced by employing an electrically conductivebacking material as a backing layer, or by adding electricalconductivity enhancers, such as powdered graphite and acetylene blackhomogeneously mixed therewith, or by using a high surface area materialwhich itself is intrinsically, highly electrically conductive withoutany backing layer or enhancer. The high surface area material may alsobe activated carbon treated with a chemical, like alkali, such aspotassium hydroxide, or a halogen, like fluorine, to increase thesurface area and conductivity. Activated carbon material of greater thanabout 1000 square meters per gram surface area are preferred.

In one embodiment, the high surface area comprises an activated carbonfiber woven layer which provides for electrical conductivity and highporosity, although any other material which is highly electricallyconductive and which has micropores can be employed for the high surfaceactive area.

Optionally but desiredly, where the separation of certain fluids areinvolved, such as with biological fluids, proteins and organicmolecules, the high surface area material may be processed or treated toreduce the adhesion or absorption of such molecules to the high surfacematerials. Typical treatments would include the use of fluorocarbons,silicones, and other surfactant-type materials on the high surface areamaterials.

Another material which may be employed as the high surface area layercomprises a material known as azite, a black, ceramic-like substance,which is highly porous and very strong and yet electrically conductiveand is composed of a synthetic carbon polymer whose structure is flatwith holes or pores. In addition, it is desirable to provide forchemical modification of the high surface area electrically conductivelayer by the employment of adsorbing molecules thereon to alter theelectrical characteristics, such as for example, adsorbing an aromaticmolecule that contains a charge group onto the carbon cloth materiallayer which chemical modification of the surface active area may act asan ion exchanger. Azite material consists of micropores which providesuperior capacitance properties due to the elimination of one diffusionbarrier, that is, macroporous and microporous layers, and is easy tofabricate. Azite material provides for a three dimensional structure andmay thus be used alone in connection with merely a non-porous dielectricspacer to provide a flow-through capacitor. In addition, since the threedimensional structure of azite is flat with holes, convective flow rightthrough the pores of the material allows a faster method of purificationthan other materials, such as activated carbon and platinum black, wherethe porosity is on the surface, and slower processes of electrodiffusionset a limit on the speed of separation.

The insulating spacer material, usually in layer form, is placed betweenthe high surface area material to provide electrical insulation of theanode-cathode pair and is fluid porous and nonconductive to the flow ofelectrons, but which is ionically permeable or conductive to allow thepassage therethrough of ions or ionic carriers. The insulating materialmay comprise a porous woven or non-woven fibrous material composed forexample of polymeric or natural fibers or mixtures thereof, such asolefinic fibers, like polypropylene; polyamide fibers, like nylon;fiberglass; polyester fibers and fluorocarbon fibers. The insulatingmaterial may also comprise microporous, polymeric membrane materials ofionically conductive materials, such as fluorocarbon, polyamidemembranes, like Nafion® material (a trademark of E. I. Du Pont deNemours & Co.). The insulating material may also comprise nonconductiveparticles, such as ceramic, silica, polymeric or other non-insulatingmaterial particles, alone or in a mixture formed in a bed on sheetmaterial. The insulating spacer material generally has a thickness ofless than about 10 mils and a porosity or molecular cut off of less thanabout 30 microns, e.g. 10 microns or less, and requires a cut-off ofless than the molecular cut-off of the conductive high surface areamaterial.

The flow-through capacitor is composed of at least one and typically aplurality of the alternating anode-cathode units, or, if desired, may beprepared and formed in various geometric forms and may include aspiral-wound, washer or disk stacked or flat sheet comprising one layerof a high surface area material, each with or without an electricallyconductive backing layer and omitting the second insulating layer. Theanode-cathode pairs may also comprise rod or tube-like geometries. Thecomposite tubes or rods may be any geometrical shape, includingpolygons, like hexagons, square, rectangles, triangles or be circular orelliptical. Moreover, each single high surface area layer may have oneor multiple conductive solid rods or tubes running inside or through thematerial to provide greater conductivity.

Electrical leads are connected to each of the alternate anode-cathodepairs of electrodes, either connected directly to the high surface areamaterial where no conductive backing layer is used or to theelectrically conductive backing material. In one preferred embodiment,the electrical leads are integrally formed and extend from the highsurface area material or the conductive backing material, whichintegrally formed leads reduce electrical resistivity. The electricalleads connect the series of separate anode-cathode units and areconnected to a DC power supply.

The conductive backing material, such as in layer or other form, whereemployed, can be composed of any electrically conductive material, suchas a metal film, for example, of aluminum, or more particularly, of anelectrically conductive carbon, particularly graphite, in thin foilform. Where used, the high surface area electrically conductive materialis secured or placed adjacent and on both sides of the electricallyconductive backing material. Generally, the conductive backing materialcomprises a graphite foil or a conductive metal like silver or titaniumor other metal or alloys, on which palladium or platinum black iselectrodeposited to enhance the conductivity, and also selected fortheir corrosion-resistant properties. Optionally and preferably, theconductive backing material may be porous and, for example, have aplurality of holes to permit liquid flow therethrough.

The thickness of the high surface area material and the spacer materialand the conductive backing material, where employed, may vary asdesired, and generally may range, for example, from about 1.0 to 10 milsfor the conductive backing material, where employed, and from about 25to 300 mils for the high surface area material and about 10 to 100 milsfor the spacer material.

The flow-through capacitor may comprise a spirally-wound flow-throughcapacitor which comprises a plurality of spaced apart layers of theselected material with the high surface area material layers facing eachother and separated by the insulating spacer material and optionally oneither side of a conductive backing layer, the spacer material defininga flow channel to permit the flow of the fluid therethrough and thelayers spirally-wound about a hollow central core, the central coreacting as the inlet or outlet of the flow-through capacitor andtypically being porous or having a plurality of holes throughout itslength so as to permit the fluid to be separated or purified into theporous spacer layer. The flow path of the fluid may be down through thecentral core from the outside of the flow-through capacitor. Generally,the flow-through capacitor may be sealed at each end and has anode andcathode leads typically which are integral with the high surface areamaterial layer or with the conductive backing layer where employed,which leads are adapted to be connected through insulation in thehousing to a DC control power supply and control system.

In another embodiment, the flow-through capacitor may comprise aplurality of stacked washers or disks secured about a central,nonconductive porous tube or support means with the washer ends sealed.The central tube may be porous or have holes punched therein or may be arod having a plurality of longitudinal grooves therein for the passageof fluid. The washers or disks may comprise in series a first highsurface area layer separated by an insulating layer and facing a secondhigh surface area layer or where, optionally, a conductive backing isemployed, high surface area layers are secured on the opposite sides ofthe backing, and thus comprise a sequence of each anode-cathode unit ofan electrically conductive backing layer, a high surface area layer onone side of the backing layer and an insulating spacer material layer,and on the opposite side of the backing layer, a second high surfacearea layer and an insulating layer. Generally, the washers are arrangedin sequence as described and stacked about the central tube and securedtogether in a compressed, contacting arrangement for the pressure ofthreaded end caps or threaded rods on each side or other means within ahousing. The number of stacked washers may vary as desired. Theflow-through capacitor may be placed within a cartridge or a housing,such as a standard filter cartridge, with the cartridge or housinghaving a combination anode and cathode rod, for example, of graphite,extending therethrough and connected to the electrically conductive highsurface area layers alone or through the conductive backing material.The housing or cartridge includes an inlet for the introduction of thefluid to be separated. Generally, the purified liquid is then withdrawnfrom the tube at the outlet.

Where employed, the electrically conductive backing material may beemployed in film, fiber, rod, tube or foil-type form and have the highsurface area material secured or bonded and placed adjacent in anymanner on the opposite surface thereon, so that the high surfacematerial will face each other with an intervening, insulating materialin between.

The controlled charge chromatography or other system employing theflow-through cartridge may be employed for the separating of a widevariety of fluids and more particularly, any solute, solvent or liquidsystem that wants to be concentrated or purified by resolving intoseparate species. The solvent can be polar, such as water, or non-polar,such as an aromatic,-which fluid contains material which has selectivityfor the solid phase and which can be modulated by controlling the chargeof the solid phase, that is, the high surface area layer. For example,the solution may be of deionized water with resolved bands of ionicspecies, such as sodium chloride or other salts, and also any othertypes of molecules, organic, inorganic or biological. The invention willbe disclosed for the purposes of illustration in connection with theseparation of ionic liquid solutes; however, the system and method maybe advantageously employed and used in the separation of other fluids,such as, but not limited to: non-ionic solutes, like hydrophobicsolutes, or other fluids which contain one or more components whichinteract or are affected by electrically conductive surfaces, forexample, liquids containing DNA, viruses, bacteria, cells, colloids ormixtures thereof. The flow-through capacitor permits the control of thecharge on the stationary phase as the high surface area phase of theflow-through capacitor.

Typically, the spiral-wound flow-through capacitor having a central tubeemploys glue or a resin sealer at the ends for assembly and insertioninto a cartridge housing. In operation, the fluid is introduced into thecentral tube and flows radially outwardly or, more frequently, isintroduced between the exterior of the spiral-wound flow-throughcapacitor and the interior of the housing and flows radially inwardlytoward the central tube.

In another embodiment of a spiral-wound flow-through capacitor, aflow-through capacitor is assembled without the need for end glue andsealing adhesives by the use of a shrinkable, tight or snug-fittingpolymeric tube or shroud about the exterior of the flow-throughcapacitor, such as, for example, the use of a heat-shrinkable polymerwrapped about the exterior surface of the spiral-wound flow-throughcapacitor. Any shrinkable sheet material can be used generally in tubeform which is placed about the capacitor and then shrunk by theapplication of heat, radiation or other means. For example,heat-shrinkable fluorocarbon polymers, like Teflon®, or olefinicpolymers, like polyethylene, can be used. In this embodiment, thecentral tube or conduit in the spiral-wound capacitor has one or moreholes in a selected position in the tube, generally at the middle of thetube, and usually spaced apart and uniformly arranged about the tubeperiphery. The central tube is sealed at both ends instead of sealingthe capacitor layers themselves as in a typical spiral-woundarrangement. A gap is required in the surrounding high surface areamaterial layer by cutting slots or holes therein and aligning the cutholes or slots with the holes in the central tube to form a radial flowpath. In this embodiment, fluid flow passes both downwardly and upwardlyalongside the layers of the spiral-wound capacitor until the fluidreaches the central gap or hole in the central tube and the fluid iswithdrawn from the outlet at all or both ends of the central tube orconduit. This embodiment permits the easy assembly of the spiral-woundflow-through capacitor within a cartridge for use without the use ofend-sealing resins and adhesives by the use of an outside liner materialand gaps or slots in the high surface material layers aligned in a flowrelationship with holes in the central conduit.

The invention will be described for the purposes of illustration only inconnection with certain embodiments; however, it is recognized thatthose persons skilled in the art may make various modifications,changes, improvements and additions to the embodiments or illustratedembodiments, all without departing from the spirit and scope of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustrative, schematic, partially exploded view of aspiral-wound flow-through capacitor of the invention.

FIG. 2 is a schematic, illustrative, partially sectional view of thecompleted, spiral-wound, flow-through capacitor of FIG. 1.

FIG. 3 is a schematic illustration of a chromatographic column andsystem employing the flow-through capacitor of the invention.

FIG. 4 is a sectional, enlarged view through line 4--4 of FIG. 1.

FIG. 5 is a schematic, illustrative, exploded view of a stacked washerflow-through capacitor of the invention.

FIG. 6 is a perspective view of the assembled flow-through capacitor ofFIG. 5.

FIG. 7 is a fragmentary, partially sectional, schematic illustration ofa controlled charge chromatographic column of the invention with theflow-through capacitor of FIGS. 5 and 6.

FIG. 8A, B and C are top plan views of three embodiments of theconductive backing washer used in FIG. 5.

FIG. 9 is a perspective view of another embodiment of the assembledflow-through capacitor of FIG. 5.

FIG. 10 is a fragmentary, partially sectional, schematic illustration ofa controlled charge chromatographic column of the invention with theflow-through capacitor of FIG. 9.

FIG. 11 is an enlarged, fragmentary, perspective view of a plurality ofthe flow-through capacitor rods.

FIG. 12 is an enlarged, perspective, partially sectional view of aplurality of the flow-through capacitor rods of FIG. 11 within a housingcartridge.

FIG. 13 is a schematic, partially exploded, perspective view of anotherembodiment of a spiral-wound flow-through capacitor of the invention.

FIG. 14 is a schematic, partially sectional view of a fluid separationsystem with the flow-through capacitor of FIG. 13 within a housingcartridge.

DESCRIPTION OF THE EMBODIMENTS

With particular reference to FIGS. 1 and 2, there is shown aspiral-wound flow-through capacitor 10 comprised of a plurality oflayers wound about a central plastic tube 24 having a plurality ofperforations 32 therein extending down its length and having a one endwhich serves as an inlet for a fluid to be purified and an other endwhich serves as an outlet for the discharge of the purified fluid andthe ionic species. Layers 12 and 18, which may be the same or different,form a nonconductive, insulating, porous, spacer sheet material having athickness for example of about 5 mils to 50 mils, and more particularly,a layer of nylon woven cloth which forms a nonconductive spacer materialbetween the anode and the cathode. Layers 14 and 20 comprise aconductive backing layer, which optionally may have holes punchedtherein to improve flow properties, and includes integral leadsextending therefrom to act as electrical leads 28 and 30 for connectionto a power source. For example, the conductive backing may compriseUnion Carbide's Graphoil® brand 5 mils thick graphite foil with pinholes punched therethrough. Layers 16, 17, 21 and 22 are comprised of ahigh surface area conductive material, and more particularly in theillustrated embodiment, an activated carbon woven fiber cloth to form acharge-holding, conductive high surface area (for example, cloth ANF #62from Toyobo of Japan). The high surface area material layers 16 and 17and 21 and 22 are bonded to opposite sides of the conductive backinglayer 14 and 20, and directly face each other and are each separatedonly by the insulating material layers 12 and 18.

FIG. 2 is a schematic illustration of the flow-through capacitor of FIG.1 wherein the layers have been wrapped around the central tube 24wherein both ends are sealed with an epoxy resin 26 leaving open theinlet of the tube 24 and the outlet. FIG. 2 illustrates a partialsectional view that the inner tube 24 has a series of holes 32 therein,for example, 1 mm diameter holes, 1/10" apart, on a 3/16" outsidediameter tube. In another embodiment, the capacitor may have no epoxyseals, and a solid tube, so that flow is between the layers. Thecapacitor may have the top end of the hollow tube sealed so that thedirection of the flow is through the sides of the device, through thesuccessive layers, and then out the open end of the inner hollow tube.

FIG. 3 is an illustration of chromatographic column 34 and systemcontaining the flow-through capacitor 10 disposed therein and generallyaxially aligned with the axis of the column 34, the column having an endcap 36, an inlet 38 and connected to a tubing 40 for the introduction ofa fluid material to be purified, the end cap gasketed to a definedpressure, for example, up to 100 psi, and the column 34 having an outlet42. Extending from the column 34 are the conductive leads 28 and 30which have epoxy seals where the outlet tubing 50 and the Graphoil®leads 28 and 30 come through column 34. For example, the column 34 maycomprise a transparent, plastic, polypropylene, syringe-type barrel.Leads 28 and 30 are connected to an outside power supply and control 56.

FIG. 4 is an enlarged sectional view of the flow-through capacitor ofFIG. 1 illustrating that the respective high surface material layers 16,17, 21 and 22 on opposite sides of separate, conductive backing materiallayers 14 and 20 and facing each other, but separated by the insulatinglayers 12 and 18, to provide an effective, improved flow-throughcapacitor with a pair of anode-cathode units.

The spiral-wound flow-through capacitor of FIGS. 1-4 was preparedemploying as the high surface area material two 8"×3" pieces of 4 gramseach of activated carbon cloth (American Kynol Co. of Pleasantville,N.Y. ACC-509-20) as the insulating spacer material, two 3"×5" pieces ofnylon cloth 2 micron pore size (Tetko 3-5/2) and as the conductivebacking layer, two 3"×4" pieces of a 5 mil graphite foil material(polycarbon). The activated carbon cloth was folded over the conductivegraphite foil and the insulating material placed on either side and thelayers then spiral-wound about a 3" long 1/4" OD plastic tube with holestherein, the tube ends sealed, and the device placed in a pressure tight30 cc syringe barrel as a cartridge, and a DC voltage of 2 volts appliedto the conductive material leads. The device purified a 0.01M sodiumchloride solution to better than 90% purity at a flow rate of 14ml/minute at 2 volts. The recovered sodium chloride peak was greaterthan 0.05M concentration. A 0.1M sodium chloride solution was purifiedat 1 ml/minute to better than 80% purity. A flow capacitor usingidentical quantities of activated cloth but spiral-wound in alternatinglayers as in U.S. Pat. No. 5,192,432 with a flow rate of 14 ml/minuteand 0.01M sodium chloride solution feed provided only 60% purificationrather than 90% purification with the face-to-face, high surface areaembodiment as shown.

FIG. 5 shows a stacked washer flow-through capacitor 100 in an explodedform having a rubber washer 102 at the top end thereof to form awatertight seal when the capacitor 100 is put inside a standard filtercartridge holder 136 (see FIG. 7). The cartridge 100 contains end caps106 made of an inert, nonconductive material, such as for example, ahigh density polypropylene resin, with the end caps threaded on theinside to screw onto threads 108 on the end of a central tube 110. Thetop end cap includes two concentric circles of inert conductive material104, such as for example, but not limited to: gold, gold foil, graphiteor platinum series metals and the like. The central supporting tube 110comprises a porous polyethylene tube, for example a 10-inch tube ofporous plastic with a 3/8" outside diameter and a 1/8" wall thickness.The central tube 110 acts as a supporting member to hold the ring-shapedor washer parts together and under compression when the end caps 106 arethreadably screwed against the ends of the central tube 110. The porousplastic tube 110 allows for flow out of the middle of the tube to thetop end. The tube could also include a solid, rod-like element withlongitudinal, fluted sides to provide support for the washer elementsand also provide for flow out of the tube. Employment of a central,plastic, porous, polyethylene tube has the added advantage of being alsoa microfilter, for example, of one to five microns or less, so as tofilter out any fine material which may leach off a carbon disk or otherwasher materials. The cartridge 100 includes a plurality of washermaterials in sequence to include a porous, nonconductive spacer materialwith pores, for example, a synthetic, fibrous material or other type ofnonconductive spacer material, such as fiberglass or woven nylon.

Washer material 120 comprises any inert, conductive backing material,for example, a 5-mil thick Graphoil® brand (Union Carbide graphite foilmaterial) with multiple holes 119 perforated in it to provide for betterliquid flow therethrough. This graphite foil material (also see FIG. 8)provides a pair of washer materials 120 connected with a connectingbridge 115 having an optional notch 114 to accommodate electricalcommunication to a conductive material. The tab or arm 115 connectingthe two halves of the backing material 120 provides for the connectingtab or arm 115 to be crimped to form tabs that extend outside of thecompleted, assembled flow-through cartridge, which tabs can then beutilized for form conductive leads. In one preferred embodiment, theconductive leads having charge may be faced inwardly.

The washer material 116, 117, 121 and 122 comprises any high surfacearea conductive material. One example is the use of KX Industriesextruded, activated carbon tubes which are held together with a smallamount of polypropylene binder. These tubes are extruded in tube shapes2" overall in diameter with an inner diameter which is widened to 13/8"and cut into rings of about 1/8" thickness. Such high surface areaconductive material 120 may also include activated carbon cloth full ofactivated carbon fibers, since the compression afforded by the stackedwasher cartridge flow design would compress the loose material and allowit to become conductive by inner particle contact, thus allowing thechoice of other inexpensive, conductive, high surface area conductivematerials.

The conductive leads material 126, as shown on the right hand side ofthe exploded diagram in FIG. 5, includes folded tab 128 which can bemade of any electrically conductive material, such as for example,Graphoil®, or may also be a wire (as shown in FIG. 9) suitably coated toprotect it from the environment or a naked inner wire of gold orplatinum, along with the electrically conductive material, could beattached by a clamp 130 to the arm 118 or tab 132. The conductivematerial as illustrated in FIG. 5 is shown in corrugated form. The flattab section 128 is designed to lie on top of pans 120 or 116, 117, 121and 122 to form an electrical contact under compression. As illustrated,an optional notch 114 can be employed to accommodate thickness of thetab, while in many cases the other materials are compressible enough sothis added notch need not be employed. The conductive leads 126 and tabs128 short together the alternating layers composed of conducting layers116, 117, 121 and 122 and 120 which are separated by the insulatingspacer 112 and 118 to form alternating washer anodes and cathodes up anddown the central tube 110.

FIG. 6 shows the assembled flow-through capacitor cartridge 100 showingthe side leads 124 that short the alternating anode and cathode washerlayers together in parallel. The tabs 128 are now pressed against thebacking layers 120 to form electrical contact. The conductive leads 124are also electrically connected on each of the conducting circles 104 inthe end cap 106. The assembled flow-through capacitor cartridge 100 asillustrated in FIG. 6 is thus ready for insertion in a standard filtercartridge for use as a controlled charge chromatography system.

FIG. 7 is a fragmentary, partially sectional, schematic illustration ofa controlled charge chromatography apparatus showing the use of theflow-through capacitor cartridge 100 within a standard filter cartridge136 having a screw-on head 138 with the inlet 150 for the introductionof a liquid for a controlled charge chromatographic separation, and anoutlet 152 for the removal of a purified liquid from the center of thecentral supporting tube 110. The cartridge head 138 is modified to allowwatertight, electrically conductive leads 148 to an outside power supplywith the employment of paired conductive rods, for example 3/8" graphiterods 144 and 146, having pointed ends, which are in electrical contactwith the concentric circles 104 and the end caps 106 of the cartridge100, with compression nuts used to form a watertight seal over the rods144 and 146. Threaded inserts go in to the filter holder cartridge top138 to corresponding threaded holes in the top cover for the employmentof the rods 144 and 146 in a watertight fashion. The rods have leads 148to a power supply (not shown, but see FIG. 3). The filter holder top 138is screwed tightly to form a watertight seal against washer 102. Theconductive rods 144 and 146 are pressed firmly against the concentricconducting circles 104, thereby forming electrical contact through tothe leads 124. Since the washers are concentric, no matter how the topis screwed on, the rods 144 and 146 will always be positioned in theright place against conductive circles 104.

In operation, a liquid to be purified is introduced through inlet 150,150 flows to the outside within cartridge 136, and goes through from theinside to the outside of the washer 102. Purified liquid is then removedthrough the central tube 110 and therefore through outlet 152. While theconductive backing material has been described in a particular form,that is, two washers 120 with a conducting arm bridge 115, thisparticular form is not essential to the operation of the flow-throughcapacitor of the invention, and obviously may be replaced by otherforms, but the illustrated form represents one preferred embodimentemploying the electrically conductive backing material in the stackedwasher flow-through capacitor of the invention.

FIG. 8 shows three types of electrically conductive backing washers A, Band C. FIG. 8C shows a conductive backing washer 120 connected byconnecting tab 115 with an optional notch 114, and multiple holes 119perforated in it to provide for better liquid flow-through. FIGS. 8A and8B show separate electrically conductive backing washers for layers,with FIG. 8A showing the optional notch 114 to accommodate electricalcommunication to a conductive material and FIG. 8B showing an extendedtab 132 for attachment by clamp 130 of an electrically conductive wireor lead 134. Thus, as illustrated, a new, improved and uniqueflow-through capacitor and controlled charge purification chromatographycolumn system and method have been discovered which provide for theeffective and rapid separation by a flow-through capacitor of highelectric capacitance and high surface area, high adsorption ability,electrically conductive, stationary phase in the chromatographic column.

FIG. 9 shows another embodiment of the flow-through capacitor 105showing the tab arms 132 extending from the compressed washer assemblywith electrically conductive clamps 130 connected to each other by anelectrically conductive wire 164, which leads from the capacitor to apower supply by lead lines 154 and 155 on either side of the capacitor105. The assembled flow-through capacitor cartridge 105 is thus readyfor insertion in a standard filter cartridge for use as a controlledcharge chromatography system.

FIG. 10 is a fragmentary, partially sectional, schematic illustration ofa controlled charge chromatography apparatus showing the use of theflow-through capacitor cartridge 105 within a standard filter cartridge136 having a screw-on head 138 with inlet 150 for the introduction of aliquid for a controlled charge chromatographic separation, and an outlet152 for the removal of a purified liquid from the center of thesupporting tube 110. The cartridge head 138 is modified to allowwatertight, electrically conductive leads 154 and 155 to extend to anoutside power supply (not shown) through holes 158. Threaded screws 160screw into the filter holder cartridge top 138 through holes 156 tocorresponding threaded holes 157 in the top cover 106 to seal the coverin a watertight fashion against washer 102.

FIGS. 11 and 12 illustrate an optional geometric form of theflow-through capacitor in a compact electrode bundle configuration 162.FIG. 11 illustrates the electrode bundles 166 consisting of high surfaceconductive material 170 with an optional conductive backing rod 174 withcentral hole 175 and side holes 176 to provide a fluid flow path intoand radially through the high surface area material 170, surrounded andconnected by ion permeable, non-electrically conductive spacer material168 and individual lead lines 164 extending from the central holes 175in the rods 174. The side holes 176 may be replaced, if desired, with agroove extending vertically along the rod 174. An electrical connectorcomposed of a pair of cap-shaped metal clamps 165 at the end ofelectrical lead 164 is used to connect the ends of the graphite rods.

FIG. 12 is a perspective, partially sectional view of a plurality ofelectrode bundles 166 within a holder cartridge 136 with a screw-on top138 having an inlet 180 for the fluid feed stream and an outlet 192 forthe purified liquid. The individual electrode bundles 162, withconductive backing rods 174 extending therefrom are connected byelectrically conductive lead lines 164 extending from the rods, whichlead lines are then gathered into main lead lines 186, which pass outfrom the cartridge holder 136 to the power supply. The compact electrodebundle configuration 162 is held together by shrink wrapped teflon 188applied to the outside of the bundles, and further by watertight gaskets190 to seal the electrode bundle against the cartridge holder wall.

FIGS. 13 and 14 show a further embodiment of the spiral-woundflow-through capacitor assembly as shown in FIG. 1, comprised of aplurality of layers 12, 14, 16, 17, 18, 20, 21 and 22 wound about acentral plastic tube 24 with end caps 106 to seal the ends of the tube,and an outlet fluid feed 196. The conduit 24 has a plurality of holes200 evenly spaced around the circumference and at the mid-point of thecentral tube 24. Corresponding slots 202 are cut in the middle of thehigh surface area conductive material 16, 17, 21 and 22, which slots,when wound around the central tube 24, creme a flow path for the liquidto be purified to pass through the filter layers. FIG. 14 shows theflow-through capacitor of FIG. 13 in a cartridge holder 136 with ascrew-on lid 138 having two holes 220 in the lid to allow the mainanode-cathode leads watertight egress to outside power supply, and afluid inlet tube 204 and outlet 196. The spiral-wound capacitor assembly194 is sealed by a shrink wrap with a teflon liner 188 and furtherwrapped by a plastic pipe 218. When wound in this manner, the slots 202cut into the middle of high surface area conductive material layers 16,17, 21 and 22 form gaps 210 which align with the holes 200 in theconduit tube 24, to allow the fluid to flow out through the center.Conductive leads 28 and 30 extend from the spiral-wound capacitorconfiguration to clamps 216 which attach the leads to the main anodelead 212 and main cathode lead 214 through holes 220 in the lid 138 tothe power supply and control. With the spiral-wound flow-throughcapacitor shrink-wrapped in the teflon seal, the system does not requiresealing caps or glue on the ends. In this manner the fluid is introducedthrough fluid inlet 204 and is passed both downward and upward alongsidethe layers until it reaches the central gap 210. It then travels throughthe holes 200 into the conduit tube 24, and then out through the outlet196.

What is claimed is:
 1. A flow-through electrical capacitor having atleast one anode and cathode pair and adapted for use in a housing as acartridge for use in the electrical separation of fluids containingionic components, which capacitor comprises:a) an ionically permeable,electrically insulating spacer material layer to permit the flow of ionstherethrough and into contact with the anode and the cathode; b) aporous, first high surface area, electrically conductive material layerto act as a stationary phase anode; c) a porous, second high surfacearea, electrically conductive material layer to act as a stationaryphase cathode; d) the first and second high surface area, electricallyconductive material layers disposed to face each other externally oneither side of the spacer material; e) a first electrically conductivebacking material layer: f) a second electrically conductive backingmaterial layer; g) the first and second electrically conductive backingmaterial layers disposed externally and in electrical contactrespectively with the first and second high surface area, electricallyconductive material layers; and h) electrical lead means adapted toconnect the first backing and conductive material layer as an anode andthe second backing and conductive material layer as a cathode to asource of electrical power.
 2. The capacitor of claim 1 which includes aplurality of alternating anode and cathode pairs which capacitorincludes first and second high surface area, electrically conductivematerial layers disposed externally and in electrical contact withopposite sides of each backing material layer and with first and secondelectrically conductive material layers disposed to face each other oneither side of the spacer material.
 3. The capacitor of claim 1 whichincludes a plurality of alternating anode and cathode pairs each ofwhich pairs comprises:a) a porous, first electrically conductive, highsurface area material layer: b) a porous, second electricallyconductive, high surface area material layer; c) a first electricallyconductive backing material layer; d) the first and second high surfacearea material layers disposed externally on either side of the firstbacking material layer and in compressed electrical contact withsubstantially the total surface area of the backing material layer; ande) an ionically permeable, electrically insulating spacer material layeradjacent one surface of the first or second high surface area,electrically conductive material layers.
 4. The capacitor of claim 1wherein the electrical lead means are formed integral to the first andsecond electrically conductive backing material layers.
 5. The capacitorof claim 1 wherein the spacer material layer is selected from the groupconsisting of: fibrous sheet material; microporous polymeric membranesheet material; and particle-containing sheet material.
 6. The capacitorof claim 1 wherein the spacer material layer has a molecular cut offporosity of less than about 30 microns.
 7. The capacitor of claim 1wherein the spacer material layers each comprises a double layer wherebya fluid to be separated is introduced between the layers of the doublelayer spacer material to prevent direct initial contact of the fluidwith the adjacent high surface area material layers.
 8. The capacitor ofclaim 1 wherein the spacer material layer comprises a woven polymericsheet material having a thickness of about 10 to 100 mils.
 9. Thecapacitor of claim 1 wherein the high surface area material layer has asurface area of greater than about 1000 square meters per gram.
 10. Thecapacitor of claim 1 wherein the high surface area material layers areselected from the group consisting of:activated carbon; conductivepolymers; conductive ceramics; platinum series black; azite andcombinations thereof.
 11. The capacitor of claim 1 wherein the first andsecond electrically conductive material backing layers has holes thereinfor the passage of fluid.
 12. The capacitor of claim 1 wherein theelectrically conductive material backing layers comprise graphite ormetal foil sheet materials.
 13. The capacitor of claim 1 wherein thehigh surface area material layers have a thickness of about 25 to 300mils, and the backing material layers have a thickness of about 1 to 10mils.
 14. The capacitor of claim 1 wherein the high surface areamaterial layer comprises activated carbon or activated carbon treatedwith an alkali or a halogen.
 15. The capacitor of claim 1 wherein thehigh surface area material layers have been treated with a surfactant.16. The capacitor of claim 1 wherein the high surface area materiallayers comprise an activated carbon woven cloth, the backing materiallayers comprise a graphite sheet material and the spacer material layercomprises a polymeric layer.
 17. The capacitor of claim 1 wherein thespacer layer, high surface area layers and backing layers are in spiralwound form, and which includes an electrically-insulating, porouscentral tube on which the layers are wound about to form a spiral woundcapacitor cartridge.
 18. The spiral wound capacitor of claim 17 whichincludes an external polymeric shroud in a snug, heat-shrunkrelationship about the exterior peripheral surface of the spiral woundcartridge capacitor.
 19. The spiral wound capacitor of claim 17 whichincludes:a) a plurality of aligned, radial, generally centrally,uniformly positioned slots in the spiral wound, high surface areamaterial layers; and b) wherein the central tube includes holes thereinaligned with the said slots in the high surface area material layers.20. The capacitor of claim 1 wherein the layers are arranged in acompressed, stacked, washer column arrangement and which includes acentral porous tube having an inlet and an outlet and about which thewasher layers are arranged to form a stacked washer capacitor cartridge.21. The washer capacitor of claim 20 wherein the electrically conductivebacking material layers comprise alternating pairs of washer elements,each pair of backing washer elements integrally connected by an integralconnecting tab.
 22. The washer capacitor of claim 21 wherein the pair ofbacking washer elements have a plurality of holes in the backing washerelements, the holes positioned to extend about the central tube.
 23. Thewasher capacitor of claim 21 which includes a pair of corrugated,electrically conductive tab elements alternately longitudinally placedon the external surface of the backing washer elements to formcontinuous connecting anode and cathode electrical lead means.
 24. Thecapacitor of claim 1 which comprises:a) a plurality of generallyparallel, longitudinal, high surface area rod elements forming a highsurface area, electrically conductive material layer; b) a plurality ofelectrically conductive, backing rod elements extending longitudinallythrough each high surface area rod element to form a backing materiallayer; c) insulating spacer material surrounding the exterior surface ofeach high surface area rod element; and d) electrical lead means at theends of each of the backing rod elements to form a plurality of separatecathode and anode pairs.
 25. The capacitor of claim 24 wherein the highsurface area rod elements are polygonal-shaped elements and arrayed in aclose, generally parallel, bundled arrangement.
 26. The capacitor ofclaim 24 wherein the high surface area rod elements are composed ofactivated carbon, and the backing rod elements are composed of graphite.27. The capacitor of claim 24 wherein the backing rod element comprisesa tube having an inlet and an outlet and a plurality of holes along thelength of the tube.
 28. A spiral wound, flow-through capacitor cartridgeadapted for use in the separation of a liquid containing ioniccomponents, which spiral wound capacitor comprises:a) a central,electrically-insulating, porous tube having an inlet or an outlet, orboth, for the passage of a liquid; b) a plurality of separate layersspirally wound about the central tube to form a capacitor and whichlayers comprise:i) an anode first and second porous, high surface area,electrically conductive material layers as stationary phases, eachhaving a surface area of greater than about 1000 m² /g, and eachcomposed of an activated carbon material; ii) a first electricallyconductive, porous backing material layer composed of a metal foil orgraphite foil material, and having an integral electrical leadtherefrom, and disposed in electrical contact with and between the firstand second high surface area material layers to form an anode; iii) afirst electrically-nonconductive, porous spacer material; iv) a cathodefirst and second porous, high surface area, electrically conductivematerial layers as stationary phases, each having a surface area ofgreater than about 1000 m² /g and each composed of an activated carbonmaterial; v) a second electrically conductive, porous backing materiallater composed of a metal foil or graphite foil material, and having anintegral electrical lead therefrom, and disposed in electrical contactwith and between the first and second high surface area material layersto form an anode; vi) a second electrically-nonconductive, porous spacermaterial; and vii) the first spacer material separating layer facingadjacent the spiral wound, high surface area layers; and c) means toretain the spiral wound layers about the central tube.
 29. The spiralwound capacitor of claim 28 wherein the means to retain includes endcaps at each end of the spiral wound layers and about the inlet andoutlet of the central tube.
 30. The spiral wound capacitor of claim 28wherein the means to retain includes a heat-shrunk polymer tubularmaterial about the exterior peripheral surface of the layers.
 31. Thespiral wound capacitor of claim 30 which includes a generally centrallypositioned plurality of aligned slots in the high surface area spiralwound layers, and a plurality of generally centrally positioned,peripheral, aligned holes in the central tube with the said slots.
 32. Arod-type, flow-through capacitor cartridge adapted for use in theseparation of a liquid containing ionic components, which rod-typecapacitor comprises:a) a plurality of bundled together, generallyparallel, longitudinal rod elements having a one and the other end, eachrod element comprising:i) a porous, high surface area, electricallyconductive material to form a high surface area rod element of selectedexterior shape with an exterior surface; and ii) a central, electricallyconductive backing rod having a one and other end and within the highsurface area rod element and composed of electrically conductive backingmaterial; b) electrically insulating material extending about theexterior surface and insulating each high surface area rod element; c)the high surface exterior face layer of each rod element facing anotherexterior face surface of an adjacent high surface area rod element andseparated only by the spacer material; d) means to connect electricallythe one or other end of each central backing rod to a source ofelectrical power to form a plurality of adjacent, alternating anodes andcathodes of the rod elements; and e) means to retain the rod elements inan arrayed, bundled cartridge form.
 33. The rod-type capacitor of claim32 wherein the central rod comprises a tube having a one and other endfor the passage of a liquid therethrough.
 34. The rod-type capacitor ofclaim 33 wherein the central tubes of each rod element have a pluralityof holes along the length of the central tube.
 35. The rod-typecapacitor of claim 32 wherein the high surface area material comprisesactivated carbon, and the central backing rod comprises a metal orgraphite material.
 36. The rod-type capacitor of claim 32 wherein therod element comprises a hexagonal-shaped rod element.